tools: add Zippy test utility

[marksvc]

This change is 

[marksvc]

When testing #3628 I found it helpful to be able to test a scenario using an unzipping tool that used SharpZipLib. (And in combination with another zip tool.)

It may be useful to retain the tool for future testing/experimenting as well.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.82%. Comparing base (9ccc759) to head (f51456b).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #3629   +/-   ##
=======================================
  Coverage   82.82%   82.82%           
=======================================
  Files         609      609           
  Lines       37426    37426           
  Branches     6159     6154    -5     
=======================================
  Hits        30998    30998           
+ Misses       5494     5481   -13     
- Partials      934      947   +13     

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